The life expectancy of people going to Mars may be decreased by the higher level of radiation that they receive.

The big companies are the private industry. But they're faced with a short-term need to show a profit in short-term.

The universe is the way it is. It's not going to be changed by supplications.

Timing has always been a key element in my life. I have been blessed to have been in the right place at the right time.

I don't think we're going to build a 50-person spacecraft or a 100-person spacecraft.

When we set out to land people on the surface of Mars, I think we should as a nation, as a world, commit ourselves to supporting a growing settlement and colonization there. To visit a few times and then withdraw would be an unforgivable waste of resources.

Globalisation means many other countries are asserting themselves and trying to take over leadership. Please don't ask Americans to let others assume the leadership of human exploration. We can do wonderful science on the Moon, and wonderful commercial things. Then we can pack up and move on to Mars.